Maximum dose of IV Phenytoin (maintenance)

Status Epilepticus

• Loading dose at 15-20mg/kg (diluted in a 100ml NS at a rate of <50mg/min and <25mg/min in elderly and cardiac disease)

• Additional loading dose of 2-10mg/kg  may be required in some (max 30mg/kg)

• Maintenance is at 5mg/kg/day oral/IV after 12hour of loading dose OR IV 100mg TDS- QID.

• When treatment with oral phenytoin is not possible, IV dose can be substituted for the oral dose at the same total daily dose. As the oral capsules have a an availability at 90%, serum concentrations need to be monitored closely. There is an expected increase by ~8% for oral to IV conversion, thus appropriate dosage adjustment may be necessary.

• Due to higher risks of cardiac and local toxicity associate with IV dosing, oral dosing should be used whenever possible.

Neurosurgery (Prophylactic)

• 100 to 200 mg IM at about 4 hour intervals during surgery and the immediate postoperative period. (Note: While the manufacturer recommends IM administration, this route may cause severe local tissue destruction and necrosis. Some clinicians recommend the use of fosphenytoin if IM administration is necessary.)

•  If IM administration is not necessary, accepted protocol has been 100 to 200 mg IV at about 4 hour intervals during surgery and the immediate postoperative period

Reference:

1. Lexicomp

2. http://www.accessdata.fda.gov/drugsatfda_docs/label/2011/010151s036lbl.pdf

3. http://www.drugs.com/dosage/phenytoin.html